Aerobic exercise is a popular form of exercise that improves one's cardiovascular health by reducing blood pressure and providing other benefits to the human body. Aerobic exercise generally involves low intensity physical exertion over a long duration of time. Generally, the human body can adequately supply enough oxygen to meet the body's demands at the intensity levels involved with aerobic exercise. Popular forms of aerobic exercise include running, jogging, swimming, and cycling among others activities. In contrast, anaerobic exercise often involves high intensity exercises over a short duration of time. Popular forms of anaerobic exercise include strength training and short distance running.
Many choose to perform aerobic exercises indoors, such as in a gym or their home. Often, a user will use an aerobic exercise machine to have an aerobic workout indoors. One such type of aerobic exercise machine is an elliptical exercise machine, which often includes foot supports that move in fixed reciprocating directions when moved by the feet of a user. Often, the foot supports are mechanically linked to arm levers that can be held by the user during the workout. The arm levers and foot supports move together and collectively provide resistance against the user's motion during the user's workout. Other popular exercise machines that allow a user to perform aerobic exercises indoors include treadmills, rowing machines, and stepper machines, to name a few.
Another popular form of aerobic exercise is cycling. Cycling is typically done on stationary bikes indoors or on moving bikes outside that travel off road or on streets. With a traditional upright bicycle, the user rests his or her body weight entirely on a small portion of the bike's seat, handles, and pedals. With an upright bike, the user typically leans forward as he or she pedals. Another form of cycling is recumbent cycling. With a recumbent bicycle, the user is often reclined in a seat with a back support which distributes the user's weight over a larger area, including the user's back.
One type of cycling is disclosed in U.S. Pat. No. 6,497,426 issued to James L. Vanpelt, et al. In this reference, a bicycle provides a frame having forward and rear frame portions that selectively attach and detach from each other in upright and recumbent positions. In the upright position, cranks are connected to a gear box that is adapted to drive a typical chain sprocket. In the recumbent position, the cranks are removed from the rear gear box and are attached to a forward gear box. A drive shaft is positioned between the gear boxes so that the bicycle rider may power the bicycle from the forward gear box. The bicycle may also be configured to be used as a tandem with a second set of cranks attached to the rear gear box. Other types of cycling devices are disclosed in U.S. Pat. No. 6,648,353 to Pedro Pablo Cabal and U.S. Patent Publication No. 2013/0260964 issued to Benjamin Chia.